1. Field of the Invention
The present invention relates to the field of liquid crystal displaying, and in particular to a side-edge backlight module.
2. The Related Arts
Liquid crystal display (LCD) has a variety of advantages, such as thin device body, low power consumption, and being free of radiation, and is thus widely used. Most of the LCDs that are currently available in the market are backlighting LCDs, which comprise a liquid crystal panel and a backlight module. The operation principle of the liquid crystal panel is that liquid crystal molecules are interposed between two parallel glass substrates and a plurality of vertical and horizontal fine electrical wires is arranged between the two glass substrates, whereby the liquid crystal molecules are controlled to change direction by application of electricity in order to refract out light emitting from the backlight module for generating images. Since the liquid crystal panel itself does not emit light, light must be provided by the backlight module in order to normally display images. Thus, the backlight module is one of the key components of an LCD. The backlight module can be classified in two types, namely side-edge backlight module and direct backlight module, according to the position where light gets incident. The direct backlight module comprises a light source, such as a cold cathode fluorescent lamp (CCFL) or a light-emitting diode (LED), which is arranged at the back side of the liquid crystal panel to form a planar light source that directly provides lighting to the liquid crystal panel. The side-edge backlight module comprises a backlighting source of an LED light bar arranged at an edge of a backplane that is located rearward of one side of the liquid crystal panel. The LED light bar emits light that enters a light guide plate (LGP) through a light incident face of the light guide plate and is projected out through a light emergence face of the light guide plate, after being reflected and diffused, to thereby pass through an optic film assembly to form a planar light source for the liquid crystal panel.
The side-edge backlight module is of increasing wide applications due to the advantages of relatively low manufacturing cost and being capable of arranging a slim bezel for the liquid crystal display device. Referring to FIG. 1, a cross-sectional view is given to show a backlight source of a conventional side-edge backlight module bonded to an aluminum-extruded heat sink. Since a backlighting LED light bar 100 itself generates a great amount of heat, it must be bonded to an aluminum-extruded heat sink 500 via double-sided thermally-conductive tape 300. To lower down cost and reduce the area of a printed circuit board (PCB) 102 of the backlighting LED light bar 100, the PCB 102 is made in the form of a blade and the blade is partially inserted into the aluminum-extruded heat sink 500. The aluminum-extruded heat sink 500 forms an open slot in a corresponding portion thereof. Due to the limitation of manufacturing, burrs 508 are easily formed between a bottom board 504 and a side board 506 of the aluminum-extruded heat sink 500, leading to poor parallel and flat positioning of the PCB 102 to the side board 506 of the aluminum-extruded heat sink 500. Consequently, an angle is formed between a light emission surface of the backlighting LED light bar 100 and an incidence surface of a light guide plate (not shown), and the utilization rate of light is affected, leading to deterioration of illumination quality of the module. If additional processing is made on the aluminum-extruded heat sink, then CNC processing is necessary. This increases cost and lowers efficiency to thereby affect throughput.